Re: GDK_POINTER_MOTION_HINT_MASK has no effect

["Richard Boaz" <riboaz@xxxxxxxxx>]

Hi,

I'm not really sure what is_hint is intended to provide, but anyway, what
you are trying to achieve is totally possible without its use (if I
understand you properly).

Going on the assumption I do understand what you are trying to achieve, I
am providing below some code to illustrate this.  Though actual code, it
is not runnable in its stand-alone form, you will need to tweak it a bit
to make it actually work.  However, it does contain all the hooks
necessary to do the following:

   1. Draw a solid line from point A to point B:
      point A = point at mouse-down
      point B = point at mouse-up
   2. Draw a dashed line from point A (same as in 1) to Drag Point B:
      Drag Point B = point at drag event callback

I have left out the configure and expose callbacks, I assume that these
have been called and produce a pixmap for display, this pixmap being held
in the global variable DAcontents.  (Again, this is to illustrate, not to
demonstrate proper coding, you probably shouldn't make a global variable
for this purpose.)

The mouse event callback:

   1. On mouse-down, save the starting point (point A)
   2. On mouse-up, draw a solid line from point A to the ending point
(point B) and render to the screen.

The drag event callback:

   1. If mouse is not down, do nothing and return
   2. If mouse is down, create temporary pixmap and copy DAcontents to it
   3. draw a dashed line from point A to Drag Point B (event->x, event->y)
on our temp pixmap
   4. Render temp pixmap to the screen
   5. unref temp pixmap
   6. call gdk_window_get_pointer() to tell the main loop we are done with
the drag event and are ready to receive another call to the drag event
callback

Not sure where the problem is in your implementation, but doing these
sorts of things with GTK+ is typically not problematic.

cheers,

richard

========= begin code ===================

GdkPixmap    *DAcontents;
GdkGC        *gcMain;

int main(int argc, char **argv)
{
    GtkWidget    *da;

    gtk_init(&argc, &argv);

    da = gtk_drawing_area_new();
    g_signal_connect (da, "button_press_event", G_CALLBACK (doMouse), NULL);
    g_signal_connect (da, "button_release_event", G_CALLBACK (doMouse),
NULL);
    g_signal_connect (da, "motion_notify_event", G_CALLBACK (doDrag), NULL);
    gtk_widget_set_events (da, gtk_widget_get_events (da)
                              | GDK_BUTTON_PRESS_MASK
                              | GDK_BUTTON_RELEASE_MASK
                              | GDK_POINTER_MOTION_MASK
                              | GDK_POINTER_MOTION_HINT_MASK);
    gtk_main();
}

int    startX, startY, endX, endY;
gboolean mouseDown;

gboolean doMouse(GtkWidget *da, GdkEventButton *event, gpointer nothing)
{
    if (!gcMain)
        gcMain = gdk_gc_new(da->window);

    switch(event->type)
    {
        case GDK_BUTTON_PRESS:
            startX = event->x;
            startY = event->y;
            mouseDown = TRUE;
        break;
        case GDK_BUTTON_RELEASE:
            endX = event->x;
            endY = event->y;
            gdk_draw_line(DAcontents, gcMain, startX, startY, endX, endY);
            gdk_draw_drawable(da->window, da->style->fg_gc[GTK_STATE_NORMAL],
                                DAcontents, 0, 0, 0, 0, -1, -1);
            mouseDown = FALSE;
        break;
    }
    return TRUE;
}

gboolean doDrag (GtkWidget *da, GdkEventMotion *event, gpointer nothing)
{
    GdkModifierType     state;
    gint                x, y;
    GdkPixmap            *pixmap;
    static GdkGC        *gcDash=NULL;

    if (!gcDash)
    {    // first time call setup
        gcDash = gdk_gc_new(da->window);
        gdk_gc_set_line_attributes(gcDash, 1, GDK_LINE_ON_OFF_DASH, 0, 0);
    }

    switch(mouseDown)
    {
        case FALSE:
        break;

        case TRUE:
            pixmap = gdk_pixmap_new(da->window, da-> allocation.width,
da->allocation.height, -1);
            gdk_draw_drawable(pixmap, da->style->fg_gc[GTK_STATE_NORMAL],
DAcontents,
                        0, 0, 0, 0, -1, -1);
            gdk_draw_line(pixmap, gcDash, startX, startY, event->x,
event->y);
            gdk_draw_drawable(da->window, da->style->fg_gc[GTK_STATE_NORMAL],
                                pixmap, 0, 0, 0, 0, -1, -1);
            g_object_unref(pixmap);
        break;

    }

    gdk_window_get_pointer(event->window, &x, &y, &state);
    return TRUE;
}

========= end code ===================

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